This application relates generally to the art of molding and, more particularly, to foundry sand molding apparatus of the type wherein sand molds are formed by squeezing sand between a head and table. However, it will be appreciated that certain aspects of the invention may be used in apparatus of other types.
Apparatus for making foundry sand molds commonly include a head and table between which sand is squeezed to form a sand mold. A flask positioned on the table in surrounding relationship to a pattern is filled with sand, and the sand is then squeezed between the head and table to form the sand mold.
In the most common apparatus of the type described, and particularly apparatus for green sand molding, the squeeze board on the head is essentially flat and the flask is substantially filled with sand. The rear surface of the resulting sand mold, opposite from the front or cavity forming surface, is substantially flat. The mold also varies in thickness between its front and rear surfaces. This arrangement is rather wasteful of sand because a large volume of sand is required for each mold. The resulting molds are also very heavy and bulky, and this complicates handling of same. Therefore, shell molding techniques have been developed for manufacturing shell molds having a rear surface which generally follows the contour of the front surface. The mold has a substantially constant thickness between its front and rear surfaces. Shell molds are manufactured in several different ways, including spreading a substantially uniform layer of chemical or resin bonded sand over a pattern and then curing the sand. Shell molds are also manufactured by the use of squeeze boards having a contour generally corresponding to that of the pattern. The substantially mating squeeze board and pattern define a cavity between them of substantially uniform thickness. This manufacturing procedure can be used with green sand molding, or with chemical or resin bonded sand. It is also known to produce shell molds by using a flexible diaphragm which is forced by air pressure against a pattern for compacting sand located between the diaphragm and pattern. The diaphragm will generally correspond to the shape of any pattern for producing a shell mold.
With apparatus of the type described using squeeze boards shaped to correspond generally with the pattern contour, it is usually necessary to have different squeeze boards for the cope and drag sand mold sections. Therefore, two molding machines are required for producing the cooperating cope and drag sand mold sections so they can be poured in an orderly and efficient manner. The requirement of having two molding machines makes the operation very expensive, and occupies a large amount of valuable space in a manufacturing facility. It is not efficient to use a single machine for manufacturing a plurality of cope mold sections and then shut the machine down for changing the squeeze board to manufacture a corresponding number of drag mold sections. It would be desirable to have a foundry sand molding apparatus which was capable of efficiently manufacturing different cope and drag sand mold sections.
In conventional foundry sand molding apparatus, sand is simply supplied to the flask with little regard to uniform sand distribution. However, when using squeeze boards shaped to the same general contour as the pattern, it is desirable to have a more uniform distribution of sand covering the pattern.